#include <stdio.h>
#define MAXBUFF 100

void ignore_line(void);
int ignore_multiline(void);
int pass_char_const(char fst);
int pass_string(char fst);

int flush_buff(char buff[], int bi);
int is_blank(char c);

/* remove comments from input; remove empty lines and trailing spaces 
 * left by removed comments; Check for the following errors:
 * - invalid string literals
 * - invalid char constants
 * - non-terminating multi line comments */
int main()
{
    int a, b;

    int bi = 0; // blank buffer index
    char blank_buff[MAXBUFF]; // blank buffer
    
    for (a = getchar(); (b = getchar()) != EOF; a = b)
        if (a == '/' && b == '*') {
            bi = 0;
            if (ignore_multiline()) {
                printf("\nerror : no terminator for multiline comment\n");
                return 1;
            }
            b = getchar();
        } else if (a == '/' && b == '/') {
            bi = 0;
            ignore_line();
            putchar('\n');
            b = getchar();
        } else if (a == '\'') {
            bi = flush_buff(blank_buff, bi);
            putchar('\'');
            if (pass_char_const(b)) {
                printf("\nerror : invalid character constant\n");
                return 1;
            }
            b = getchar();
        } else if (a == '"') {
            bi = flush_buff(blank_buff, bi);
            putchar('"');
            if (pass_string(b)) {
                printf("\nerror : invalid string literal\n");
                return 1;
            }
            b = getchar();
        } else if (is_blank(a)) {
            if (bi >= MAXBUFF)
                bi = flush_buff(blank_buff, bi);
            blank_buff[bi] = a;
            ++bi;
        } else if (a == '\n') {
            flush_buff(blank_buff, bi);
            blank_buff[0] = a;
            bi = 1;
        } else {
            bi = flush_buff(blank_buff, bi);
            putchar(a);
        }

    if (a != EOF)
        putchar(a);

    return 0;
}

/* ignore line of input */
void ignore_line()
{
    int c;
    while ((c = getchar()) != EOF && c != '\n')
        ;
}

/* ignore input until comment termination occurs
 * return 1 if error otherwise 0 */
int ignore_multiline()
{
    int a, b;
    for (a = getchar(); (b = getchar()) != EOF; a = b)
        if (a == '*' && b == '/')
            return 0;
    return 1;
}

/* pass the tail of a character constant from input to ouput 
 * return 1 if error otherwise 0 */
int pass_char_const(char fst)
{
    int c;

    putchar(fst);
    if (fst == '\\') {
        if ((c = getchar()) == EOF)
            return 1;
        putchar(c);
    }
    if ((c = getchar()) == EOF || c != '\'')
        return 1;
    putchar(c);
    return 0;
}

/* pass the tail (wihtout fst element) of a
 * C string literal from input to output.
 * 'fst' is the first character of the string tail
 * return 1 if error otherwise 0 */
int pass_string(char fst)
{
    int snd;

    putchar(fst);
    for (; (snd = getchar()) != EOF; fst = snd) {
        putchar(snd);
        if (fst == '\n')
            break;
        if (snd == '"' && fst != '\\')
            return 0;
    }
    return 1;
}

/* print buffer 'buff' and return 0 */
int flush_buff(char buff[], int bi)
{
    printf("%.*s", bi, buff);
    return 0;
}

int is_blank(char c)
{
    return c == ' ' || c == '\t' || c == '\b';
}